Field of Invention
The present invention relates to an inhaler.
Description of Related Art
The present invention specifically relates to active inhalers such as an inhaler sold by the assignee of the present application under the trademark RESPIMAT®, as illustrated in its basic structure in WO 91/14468 A1 (corresponding to U.S. Pat. No. 5,497,944) and in a specific embodiment in WO 97/12687 A1 (corresponding to U.S. Pat. No. 5,964,416; FIGS. 6a, 6b). The inhaler has, as a reservoir for a fluid which is to be atomized, an insertable rigid container having an inner bag containing the fluid and a pressure generator with a drive spring for delivering and atomizing the fluid.
The invention also relates to powder inhalers, whether multidose pre-metered or reservoir devices.
To supplement the disclosure of the present application reference is made to the complete disclosure of both U.S. Pat. Nos. 5,497,944 and 5,964,416. Generally, the disclosure contained therein preferably relates to a inhaler with a spring pressure of 5 to 200 MPa, preferably 10 to 100 MPa on the fluid, with a volume of fluid delivered per stroke of 10 to 50 μl, preferably 10 to 20 μl, most preferably about 15 μl. The fluid is converted into an aerosol the droplets of which have an aerodynamic diameter of up to 20 μm, preferably 3 to 10 μm. Furthermore, the disclosure contained therein preferably relates to a inhaler of cylindrical shape about 9 cm to about 15 cm and about 2 cm to about 5 cm wide and with a jet spray angle of 20° to 160°, preferably 80° to 100°. These values also apply to the inhaler according to the teaching of the present invention as particularly preferred values.
Active inhalers in the sense of the present invention generate the desired aerosol of the inhalation formulation by means of a conveying means, such as a propellant, a pump, an air pump or any other pressure generator or compressed or liquefied gas, i.e., not due to an air stream of a patient or user who breathes in, although the dispensing operation (aerosol operation) can be triggered by the breathing in.
When a patient puts a mouthpiece or any other end piece in his mouth and breathes in, an air stream of ambient air is sucked through the inhaler to entrain the already generated aerosol of the inhalation formulation and to discharge this aerosol. A pressure drop occurs within the inhaler when the air stream flows through the inhaler. This pressure drop depends on the flow rate and flow velocity. The flow resistance represents a quantity relating to the square root of the pressure drop at a certain flow rate. In the context of the present invention, the term “flow resistance” means the resistance which occurs when air is sucked from the mouthpiece or any other end piece of the inhaler during inhalation. In particular, the flow resistance relates to a flow path for ambient air through at least one air supply opening of the inhaler into a mouthpiece of the inhaler. More preferably, the flow resistance means the total flow resistance of the inhaler in the present invention, even if the inhaler has multiple air supply openings through which air can be sucked into the mouthpiece.
In contrast to active inhalers, where an active means generates the aerosol, passive inhalers usually have a higher flow resistance for the patient or user. This results from the fact that the generation of aerosol requires energy and, thus, leads to a respective flow resistance in passive inhalers. Nevertheless, it has been an object of the previous developments to keep the flow resistance as low as possible in both types of inhalers in order to facilitate inhalation for the patient or user.